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Re: [Amps] Supply question

To: 'Michael J Talkington' <>,
Subject: Re: [Amps] Supply question
From: Réjean Léveillé <>
Date: Wed, 20 Jul 2011 16:19:06 -0400
List-post: <">>
Hi Mike

As example I am using 2x 3-500 tubes and the HV transformer is 3 kv / 1 A
with a full bridge without a load it reaches around 3800 V, with the bleeder
resistors 2x 50 kohms/100w + 100 ohms/7w + back to back diode for the -B and
I get 3450v dc. I use an oil capacitor of 8 mfd/4 kv with 9 H choke.
At full plate current (800 mA) it will only drop 250v. This will reach the
1.7kw output. At 1kw output continuous (rtty) with the proper tube cooling
with chimney the duty cycle is 100%.
Of course this includes cage fan for the tubes, fan for all transformers and
a very small fan for the bridge and the bleeder for -20c to +50c room temp.
I have dedicated transformer for the HV, tube filament, 24v dc and the PSK
circuit. Do not omit in-rush current limiter for filament, HV at start-up
and MOV with fuses at the main ac input.

Good luck
Rejean, va2am

-----Message d'origine-----
De : [] De la
part de Michael J Talkington
Envoyé : July 19, 2011 8:48 PM
À :
Objet : [Amps] Supply question

I am building a single band hf amp. I am using two 3-500Z tubes. The specs
for the tubes say
4000 Volts dc max. I keep hearing people volting these tubes in standby
above this voltage 
and when they transmit the voltage sags to 4000 vdc or a little below. Is
this bad for the tube?
If I figure correctly 2800 volts ac full wave bridge and after filter caps I
should get  4032 volts dc
2800 X 1.44 am I correct? I will be bombarding you with questions cause I
want to do this right.
Thanks Mike N8FWD
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